refactor(ast): calculate which structs are transparent in `ast_tools` by overlookmotel · Pull Request #23958 · oxc-project/oxc

overlookmotel · 2026-06-30T00:00:29Z

Similar to #23957.

Move work from #[ast] macro into ast_tools. Calculate whether a struct can be marked #[repr(transparent)] or not in ast_tools and pass that info to #[ast] macro via the StructDetails struct. This has 2 advantages:

Avoids having to iterate over all fields of each struct in the macro.
It's more accurate. ast_tools knows the size of fields, so it can exclude ZST fields from the count.

A struct like this will now be marked #[repr(transparent)] despite having more than 1 field, because 2 of the fields contain ZSTs:

struct Foo<'a> {
    num: u32,
    _empty: [u8; 0],
    _marker: PhantomData<&'a ()>,
}

Moving work from macro into ast_tools is preferable because ast_tools runs only after changes to AST, whereas the macro code runs every time oxc_ast crate is compiled.

overlookmotel · 2026-06-30T00:00:55Z

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codspeed-hq · 2026-06-30T00:10:43Z

Merging this PR will not alter performance

✅ 62 untouched benchmarks
⏩ 9 skipped benchmarks¹

_{Comparing om/06-29-refactor_ast_calculate_which_structs_are_transparent_in_ast_tools_ (ca13cdd) with main (e94b6cd)²}

9 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩
No successful run was found on main (ca13cdd) during the generation of this report, so e94b6cd was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

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overlookmotel · 2026-06-30T10:29:40Z

@claude review

graphite-app · 2026-06-30T13:04:18Z

Merge activity

Jun 30, 1:04 PM UTC: overlookmotel added this pull request to the Graphite merge queue.
Jun 30, 1:14 PM UTC: The Graphite merge queue removed this pull request due to downstack failures on PR #23948.
Jun 30, 1:14 PM UTC: The Graphite merge queue removed this pull request due to downstack failures on PR #23948.
Jun 30, 4:20 PM UTC: overlookmotel added this pull request to the Graphite merge queue.
Jun 30, 4:40 PM UTC: Merged by the Graphite merge queue.

…#23958) Similar to #23957. Move work from `#[ast]` macro into `ast_tools`. Calculate whether a struct can be marked `#[repr(transparent)]` or not in `ast_tools` and pass that info to `#[ast]` macro via the `StructDetails` struct. This has 2 advantages: 1. Avoids having to iterate over all fields of each struct in the macro. 2. It's more accurate. `ast_tools` knows the size of fields, so it can exclude ZST fields from the count. A struct like this will now be marked `#[repr(transparent)]` despite having more than 1 field, because 2 of the fields contain ZSTs: ```rust struct Foo<'a> { num: u32, _align: [usize; 0], _marker: PhantomData<&'a ()>, } ``` Moving work from macro into `ast_tools` is preferable because `ast_tools` runs only after changes to AST, whereas the macro code runs every time `oxc_ast` crate is compiled.

camc314 · 2026-06-30T14:08:33Z

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…#23958) Similar to #23957. Move work from `#[ast]` macro into `ast_tools`. Calculate whether a struct can be marked `#[repr(transparent)]` or not in `ast_tools` and pass that info to `#[ast]` macro via the `StructDetails` struct. This has 2 advantages: 1. Avoids having to iterate over all fields of each struct in the macro. 2. It's more accurate. `ast_tools` knows the size of fields, so it can exclude ZST fields from the count. A struct like this will now be marked `#[repr(transparent)]` despite having more than 1 field, because 2 of the fields contain ZSTs: ```rust struct Foo<'a> { num: u32, _empty: [u8; 0], _marker: PhantomData<&'a ()>, } ``` Moving work from macro into `ast_tools` is preferable because `ast_tools` runs only after changes to AST, whereas the macro code runs every time `oxc_ast` crate is compiled.

github-actions Bot added the A-ast-tools Area - AST tools label Jun 30, 2026

This was referenced Jun 30, 2026

feat(ast_tools): store reverse-mapping of enum inheritance in schema #23954

Merged

refactor(ast): codegen match_*! macros #23955

Merged

refactor(ast_tools): move phf::Map generation into a utility function #23956

Merged

overlookmotel self-assigned this Jun 30, 2026

overlookmotel marked this pull request as ready for review June 30, 2026 10:09

Copilot AI review requested due to automatic review settings June 30, 2026 10:09

Copilot AI reviewed Jun 30, 2026

overlookmotel force-pushed the om/06-29-refactor_ast_macros_calculate_which_enums_are_fieldless_in_ast_tools_ branch from 916651c to ee3fd99 Compare June 30, 2026 10:12

overlookmotel force-pushed the om/06-29-refactor_ast_calculate_which_structs_are_transparent_in_ast_tools_ branch from 9d0721b to e575745 Compare June 30, 2026 10:12

graphite-app Bot force-pushed the om/06-29-refactor_ast_macros_calculate_which_enums_are_fieldless_in_ast_tools_ branch from ee3fd99 to 735949f Compare June 30, 2026 13:09

graphite-app Bot force-pushed the om/06-29-refactor_ast_calculate_which_structs_are_transparent_in_ast_tools_ branch from e575745 to d9a1829 Compare June 30, 2026 13:10

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Comment thread tasks/ast_tools/src/generators/assert_layouts.rs Outdated

overlookmotel force-pushed the om/06-29-refactor_ast_macros_calculate_which_enums_are_fieldless_in_ast_tools_ branch from 735949f to e94b6cd Compare June 30, 2026 14:47

overlookmotel force-pushed the om/06-29-refactor_ast_calculate_which_structs_are_transparent_in_ast_tools_ branch from d9a1829 to a30c73f Compare June 30, 2026 14:47

Base automatically changed from om/06-29-refactor_ast_macros_calculate_which_enums_are_fieldless_in_ast_tools_ to main June 30, 2026 16:31

graphite-app Bot force-pushed the om/06-29-refactor_ast_calculate_which_structs_are_transparent_in_ast_tools_ branch from a30c73f to ca13cdd Compare June 30, 2026 16:32

graphite-app Bot merged commit ca13cdd into main Jun 30, 2026
38 checks passed

graphite-app Bot deleted the om/06-29-refactor_ast_calculate_which_structs_are_transparent_in_ast_tools_ branch June 30, 2026 16:40

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refactor(ast): calculate which structs are transparent in `ast_tools`#23958

refactor(ast): calculate which structs are transparent in `ast_tools`#23958
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